1. Field of the Invention
The present invention relates to a connector for coaxial cables, suitable for forming a strip line structure.
2. Description of the Related Art
In order to meet demands for increasing transmission speed and realizing multipurpose uses in the field of computers, it is necessary to establish impedance matching for reducing the reflection of signals and the crosstalk. Therefore, it is desirable to use coaxial cables comprising signal conductors, ground conductors surrounding the signal conductors via insulating layers, and an outer covering surrounding the ground conductors.
In the field of printed wiring boards used in computers, multi-layer printed wiring boards are used, on which signal lines are arranged in several planes, and ground (power supply) lines are arranged in the other planes, whereby the signal lines and ground lines constitute a micro-strip structure or a strip line structure. Under these circumstances, it is preferable that a connector located between the coaxial cables and the printed wiring board forms a microstrip structure or a strip line structure.
For example, U.S. Pat. Nos. 4,747,787 and 4,757,845 disclose a connector having a microstrip structure. Also, a connector having a microstrip structure is disclosed in U.S. Pat. Nos. 5,161,987, 4,616,893, 4,695,106, 4,762,500, 4,860,447, 4,860,801 and 4,907,979.
Also, a connector having a strip line structure is disclosed in U.S. Pat. No. 5,195,899.
The connector includes signal contacts connected to a signal conductor of the coaxial cables, and ground contacts connected to ground conductors of the coaxial cables. The connector can be used as a plug connector or a jack connector, and for example, male signal contacts and male ground contacts of the plug connector are respectively connected to female signal contacts and female ground contacts of the jack connector which may be provided in the printed wiring board in the computer.
In a connector having a microstrip structure, two rows of signal contacts are arranged in parallel with each other at a distance between the rows, and a row comprised of a single ground contact or multiple ground contacts (and power supply contact) are arranged between two rows of signal contacts. On the other hand, in a connector having a strip line structure, two rows of signal contacts are arranged in parallel with each other at a distance between the rows, and a row of ground contacts (and power supply contact) are arranged between two rows of signal contacts, and further, straight grounds are arranged outside of the two rows of signal contacts, so that each row of signal contacts are sandwiched between the row of ground contacts and the straight grounds. In the connector described in the above described United States Patent and having a strip line structure, the ground shell surrounds two rows of signal contacts, and this ground shell has two long and straight sides to constitute the further grounds of the strip line structure.
In the conventional connectors, the signal contacts are soldered to the signal conductors of the coaxial cables, and the ground contacts are also soldered to the ground conductors of the coaxial cables. A plurality of coaxial cables are available in the form of a flat cable or a ribbon cable in which coaxial cables are arranged in a row and coupled to each other as a unit. In order to connect signal conductors of a row of coaxial cables in the flat cable or the ribbon cable to two parallel and spaced apart rows of signal contacts, the signal conductors of the coaxial cables are alternately bent to form a V-shape, so that one signal conductor forming one leg of the V-shape is connected to the signal contact in one row and the next signal conductor forming the other leg of the V-shape is connected to the signal contact in the other row. The ground contacts are arranged at the center line of the V-shape.
In the conventional impedance matched connector, the signal conductors and ground conductors of coaxial cables are to be sorted out, and then, the signal conductors of the coaxial cables are soldered to the signal contacts, and the ground conductors of the coaxial cable are soldered to the ground contacts. Therefore, it takes much time and labor to carry out the harness work. Further, the signal contacts are soldered after the signal conductors of the coaxial cables have been alternately bent into a V-shape. Accordingly, the harness work is complicated.
Further, since the signal conductors of the coaxial cables are alternately bent and sorted out into legs of a V-shape, the pitch of the signal contacts is twice as long as that of the coaxial cables, so that the size of the connector cannot be reduced. In order that the signal contacts have the same pitch as that of the coaxial cables, for example, two flat cables must be used, and the signal conductors of coaxial cables in one flat cable are connected to one row of signal contacts, and the signal conductors of coaxial cables in another flat cable must be connected to another row of signal contacts. However, this type of connector has not been proposed.
Two parallel rows of signal contacts are arranged at a distance between the rows in the conventional connectors, however, there is no connector in which three parallel rows of signal contacts are arranged at a distance between the adjacent rows. If three rows of signal contacts are arranged parallel to each other at a distance between the adjacent rows and a row of ground contacts are disposed between the respectively adjacent two rows of signal contacts, it is possible to provide a connector in which an impedance is well matched and the size of the connector can be reduced in the direction of the row of signal contacts, and such a connector has been desired.